in many-world QM, what does it mean for the other worlds to be 'real'? What does it mean for one world to be, e.g., 1% as real as another, or that the ratio depends on the basis employed?

Can we consistently employ the Copernican/Mediocrity principle (frequentist statistics over observers) and also accept many-worlds QM?

What is dark energy?

Are we in a true vacuum or false vacuum?

Are early inflation and late inflation (dark energy) related?

Should we expect the "constants of nature" to be constant?

Are observable changes in fundamental parameters ruled out by near-constancy of vacuum energy?

If fundamental constants oscillate, how well can we constrain this?

How exactly do fundamental constants couple to vacuum transition in something like the string-theory landscape?

Why did our universe begin in a low-entropy state?

Are the relations between all of the 'arrows of time' understood?

What role, if any, does the vacuum energy play in cosmic initial conditions?

What is the nature of time in quantum physics?

To what extent can quantum physics retrodict earlier states?

Can one define Boltzmann entropy in quantum mechanics?

Is there any hope of experimentally testing quantum gravity?

Are there fundamental limits to experimentally determining the theory of quantum gravity (e.g. scattering high-energy particle may just form black holes)?

Can we devise a gedanken experiment to interfere different causal structures?

What will the ultimate theory (or at least the next one) be like?

Will it actually use the current form of QM?

Will we construct it by starting with a classical theory and quantizing it?

Will it involve tensor category theory?

As we go up in energy, should we expect to find more or less degrees of freedom?

Will the next/final theory be simple or complicated?

Beautiful or ugly?

Funny or boring?

What does it mean to understand something? Does ability to compute all answers mean that we really understand something? Or are 'emergent' phenomena just a real (and call for just as much explanation) as the processes underlying them?

Is nature fundamentally analog or digital (continuous or discrete)? - Is that a well-posed question?

Is there a continuum between discreteness and continuity?

Are there experiments in physics that really require one or the other?

Is nature completely mathematical?

If not, what would the extra ingredient(s) be?

Is 'being observed' in QM such a non-mathematical property?

Do any of our capabilities and experiences inform us that we are not in a computer simulation?

is there a Measure catastrophe (the Simulation argument)?

Does Penrose's argument have anything to say? Is there a variant that might?